The present invention relates to apparatus and/or method for calculating an intake air quantity for an engine, and more specifically to apparatus and/or method for calculating an intake air quantity in accordance with an output signal from an air flowmeter by calculating a balance between the quantity of air flowing into an intake manifold section of the engine and the quantity of air flowing out of the intake manifold section into an engine cylinder section.
A Japanese Patent Application Publication Kokai No. S61-258942 shows a system for calculating a cylinder intake air quantity from an output of an air flowmeter in an ordinary engine controlled with a throttle valve.
A Japanese Patent Application No. H11-223682 proposes a system for calculating a cylinder intake air quantity in an engine of a variable valve timing type.
In a method of calculating the mass of air flowing into an intake manifold section of an engine by integration of an air flow rate sensed by an air flowmeter, the calculation in an engine stop state where the intake air quantity is reduced to zero in theory tends to involve errors due to unit to unit nonuniformity, environmental nonuniformity such as changes in temperature, or nonuniformity in reference voltage of air flowmeter. In such a case, the integration of errors continues, and the calculation of the manifold air quantity could result in an incorrect value which could adversely influence the calculation of cylinder intake air quantity in an engine restart operation.
It is an object of the present invention to provide calculating system and/or method and engine system and/or engine control method which can eliminate undesired influence from errors caused in an engine stop state.
According to the present invention, a cylinder intake air quantity calculating apparatus for an engine comprises: a cylinder intake air volume quantity calculating section to calculate a cylinder intake air volume quantity in accordance with a cylinder volume at an intake valve closing timing, and an incylinder fresh air rate; a manifold air mass quantity calculating section to calculate a manifold air mass quantity by calculating a balance between an intake manifold inflow air mass quantity which is the mass of air flowing into an intake manifold section of the engine and which is determined from an air flow rate sensed on an upstream side of the intake manifold section, and an intake manifold outflow air mass quantity which is the mass of air flowing out of the intake manifold section into a cylinder section of the engine; a cylinder intake air mass quantity calculating section to calculate a cylinder intake air mass quantity in accordance with the cylinder intake air volume quantity, the manifold air mass quantity and a manifold volume; and a resetting section to reset the manifold inflow air mass quantity to a minimum setting value when an engine stop state having no intake air inducted into the engine is detected.
An engine system according to one aspect of the present invention comprises: an engine including an intake manifold section and a cylinder section into which intake air is inducted from the intake manifold section; an engine speed sensor to sense an engine speed of the engine; an air flowmeter to sense an intake air flow rate at a position on the upstream side of the intake manifold section; and a processing unit configured; to calculate a cylinder intake air volume quantity in accordance with a cylinder volume at an intake valve closing timing; to calculate a manifold air mass quantity by calculating a balance between an intake manifold inflow air mass quantity which is the mass of air flowing into the intake manifold section of the engine and which is determined from the air flow rate sensed by the air flowmeter, and an intake manifold outflow air mass quantity which is the mass of air flowing out of the intake manifold section into the cylinder section of the engine; and to calculate a cylinder intake air mass quantity in accordance with the cylinder intake air volume quantity, the manifold air mass quantity and a manifold volume. The processing unit may be further configured to examine whether the engine speed sensed by the engine speed sensor is within a stop range indicative of an engine stoppage; to examine whether the air flow rate sensed by the air flowmeter is within a predetermined flow rate range; and to reset the manifold inflow air mass quantity to a minimum setting value when the engine speed is within the stop range, and at the same time the air flow rate sensed by the air flowmeter is within the flow rate range. Alternatively, the processing unit may be further configured to examine whether the engine speed sensed by the engine speed sensor is within a stop range indicative of an engine stoppage; to examine whether a variation of the air flow rate sensed by the air flowmeter is equal to or smaller than a predetermined value; and to reset the manifold inflow air mass quantity to a minimum setting value when the engine speed is within the stop range, and at the same time the variation of the air flow rate sensed by the air flowmeter is equal to or smaller than the predetermined value.
According to the present invention, a cylinder intake air quantity calculating process for an engine, comprises: calculating a cylinder intake air volume quantity in accordance with a cylinder volume at an intake valve closing timing, and an incylinder fresh air rate; calculating a manifold air mass quantity by calculating a balance between an intake manifold inflow air mass quantity which is the mass of air flowing into an intake manifold section of the engine and which is determined from an air flow rate sensed on an upstream side of a manifold section, and an intake manifold outflow air mass quantity which is the mass of air flowing out of the intake manifold section into a cylinder section of the engine; calculating a cylinder intake air mass quantity in accordance with the cylinder intake air volume quantity, the manifold air mass quantity and a manifold volume; and resetting the manifold inflow air mass quantity to a minimum setting value when an engine stop state in which induction of air into the engine is stopped, is detected.
According to still another aspect of the present invention, a cylinder intake air quantity calculating apparatus for an engine, comprises: means for calculating a cylinder intake air volume quantity in accordance with a cylinder volume at an intake valve closing timing; means for calculating a manifold air mass quantity by determining a balance between an intake manifold inflow air mass quantity which is the mass of air flowing into an intake manifold section of the engine, and an intake manifold outflow air mass quantity which is the mass of air flowing out of the intake manifold section into a cylinder section of the engine; means for calculating a cylinder intake air mass quantity in accordance with the cylinder intake air volume quantity, the manifold air mass quantity and a manifold volume; and means for resetting the manifold inflow air mass quantity to a minimum setting value when an engine stop state is detected.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.